This invention relates generally to the art of packaging films and more particularly to films useful in the packaging of food products, most particularly, cheese.
At present, one common means used in the cheese making art to form large blocks of cheese is the Wincanton block former tower. The blocks formed by such tower are typically about forty pounds in weight. The blocks coming out of the tower are soft and very pliable and gelatinous in texture. As such, they tend to settle and conform to the shape of the container in which they are put. As these blocks cool and knit, they take the shape of the interior of the container.
When pouches are used in the vacuum packaging of the newly formed blocks, it has been found that excessive stiffness of the pouch film often causes broken block edges, irregular corners and wrinkled surfaces. Thus, it is preferable to provide a flexible, extensible film for use in such cheese pouches. However, the film employed must also be able to withstand significant load without seal failure and must exhibit excellent barrier properties.
Of interest is U.S. Pat. No. 4,284,674 issued to Sheptak, disclosing a multilayer film having a core layer of ethylene vinyl alcohol copolymer adhered on each side to nylon, each nylon layer in turn being adhered to a chemically modified polyolefin, and a further layer of primer material suitable to adhere the modified polyolefin to an outer layer of polypropylene or other materials suitable for conveying toughness, flex-crack resistance and moisture barrier properties to the multi-ply film.
Also of interest is U.S. Pat. No. 4,355,721 issued to Knott et al, disclosing a coextruded multilayer sheet having a first layer of nylon, an ethylene vinyl alcohol copolymer barrier layer, another layer of nylon, an adhesive layer, and another outside layer of, for example, high density polyethylene.
Of interest is U.S. Pat. No. 4,398,635 issued to Hirt, disclosing a medication package in which a coextruded multiple layer sheet may have a structure including a layer of ethylene vinyl alcohol copolymer sandwiched between adjacent layers of nylon, and in which one of the nylon layers may be further adhered to a tie resin. The nylon layers may form either an outside surface or, in one example, internal layers with additional layers of polymeric materials added to each side of the sandwich structure.
Of interest is U.S. Pat. No. 4,407,873 issued to Christensen et al, disclosing a packaging material for retort applications including a heat seal layer of linear low density polyethylene, a second layer of linear low density polyethylene with optionally 0% to 80% medium density polyethylene blended into the second layer, a third layer of anhydride modified medium density polyethylene, a fourth layer of nylon, a fifth layer of ethylene vinyl alcohol copolymer, and a sixth layer of nylon.
Of interest is U.S. Pat. No. 4,457,960 issued to Newsome, disclosing a multilayer film having a core layer of a barrier material such as ethylene vinyl alcohol copolymer and blends of such. This film may be shrinkable, may be melt extruded, and may contain outside layers having a blend of linear low density polyethylene and ethylene vinyl acetate copolymer.
Of interest is U.S. Pat. No. 4,495,249 issued to Ohya et al, disclosing a five-layer film having a core layer of a saponified copolymer of ethylene and vinyl acetate, outer layers of a mixture of linear low density polyethylene and ethylene vinyl acetate copolymer, and two adhesive layers disposed between the core layer and outer layers.
Also of interest is U.S. Pat. No. 4,683,170 issued to Tse et al, disclosing a film having a sealant layer which may be ethylene copolymer, an outer nylon blend layer, a core ethylene vinyl alcohol copolymer layer and at least one adhesive tie layer such as for adhering the core layer to the sealant layer.
Of additional interest is U.S. Pat. No. 4,746,562 issued to Fant, disclosing a multilayer film having a core layer of ethylene vinyl alcohol copolymer, two intermediate polyamide layers, outer blend layers of linear low density polyethylene and antiblock and adhesive polymeric materials adhering the outer blend layers to the respective intermediate polyamide layers.
Of further interest is U.S. Pat. No. 4,755,419 to Shah, disclosing a barrier film having an ethylene vinyl alcohol copolymer core layer, two intermediate polyamide layers, two outer layers which are either a blend of linear low density polyethylene, linear medium density polyethylene, and an ethylene vinyl acetate copolymer or a blend of an ethylene propylene copolymer and a polypropylene, and two adhesive tie layers for adhering each of the intermediate layers to a respective outer layer.
Also of interest is U.S. Pat. No. 4,956,212, issued to Bekele on Sep. 11, 1990, disclosing a peelable barrier film for vacuum skin packages and the like having a sealing layer which is either ethylene vinyl acetate copolymer or very low density polyethylene and having an abuse layer which may be a blend of ethylene vinyl acetate copolymer and very low density polyethylene.
Of related interest is U.S. Pat. No. 4,863,784, issued to Lustig et al. on Sep. 5, 1989, disclosing a heat shrinkable multilayer film with a vinylidene chloride-methyl acrylate copolymer core which further discloses an ethylene vinyl acetate/very low density polyethylene outer layer to be unacceptable.